1. Field of the Invention
Embodiments of the present invention relate to an apparatus and method for measuring displacement of an object to be measured (hereinafter, simply referred to as an “object”) in a contactless manner, and in particular, relates to measurement of displacement of an object with a laser beam.
2. Description of the Related Art
Processing with, for example, a working machine has required information regarding the position of a tool on the working machine and the shape of the tip of the tool. To determine the position of the tool and the shape of the tip thereof, a workpiece has been subjected to dummy processing and has then been detached from the working machine. Tool marks in the dummy processing have been determined with a measuring device other than the working machine, thus determining the position of the tool on the working machine and the shape of the tip thereof.
According to such a method, after dummy processing, tool marks in the dummy processing are determined outside the working machine. Disadvantageously, this leads to reduction in throughput and wearing away of the tool. In order to overcome the disadvantages, according to some related-art apparatuses and methods, a tool is allowed to block a laser beam and a change in quantity of blocked light is determined, such that displacement of the tool relative to a laser beam source is measured on a working machine in a contactless manner (refer to Japanese Patent Laid-Open No. 62-88555 and No. 2005-308605).
However, the related-art displacement measuring apparatuses and methods for determining a change in quantity of blocked light have such disadvantages that the stability of light quantity (hereinafter, referred to as “light quantity stability”) of a laser beam, light quantity distribution thereof, and deflection of the optical axis (hereinafter, referred to as “optical axis deflection”) thereof may cause a measurement error.